Flutter is an open-source UI software development kit (SDK) developed by Google, designed to help users easily create modern, high-performance applications. In this course, we will delve deeply into the fundamental concepts of Object-Oriented Programming (OOP), including class<\/strong>, object<\/strong>, and instance<\/strong>. These concepts are essential for structuring and managing Flutter applications.<\/p>\n Object-Oriented Programming (OOP) is one of the programming paradigms that manages data by grouping it as objects<\/strong>. An object includes state<\/strong> and behavior<\/strong>, and defining these objects is precisely what a class<\/strong> does. The main features of OOP are as follows:<\/p>\n Now, let’s look at how these OOP concepts are utilized in Flutter.<\/p>\n A class is a template for creating objects. A class can define data variables and may include methods that manipulate that data. Here is how to define a class in Flutter:<\/p>\n In the example above, we defined a class called An object refers to an instance of a class. In other words, it refers to a real set of data created from a class. You can create multiple objects, each having unique states. For example, we can create instances of the In the above code, we created two A class can include various components. These include constructors, methods, fields, and access modifiers. Let’s take a detailed look.<\/p>\n A constructor is called when an object is created and is responsible for initializing the object. Dart (the programming language for Flutter) supports named constructors in addition to the default constructor:<\/p>\n The named constructor provides different ways to initialize, for example, it can be used like A method is a function defined within a class. It defines the behavior the object will perform. Methods can change the state of the class or perform operations:<\/p>\n A field refers to the data variable that belongs to a class. It is used to maintain the state of the object. Fields can be categorized into instance variables and static variables:<\/p>\n Dart allows setting access restrictions on a class’s fields and methods using various access modifiers, primarily the concepts of Inheritance is the ability to create new classes based on existing ones. This makes code reuse and structural hierarchy easier. Here\u2019s an example of class inheritance:<\/p>\n In the above example, the Polymorphism refers to the ability of objects of different classes to invoke the same method. This enhances the flexibility and reusability of the code. For example:<\/p>\n1. What is Object-Oriented Programming?<\/h2>\n
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2. Class<\/h2>\n
class Car {\n String color;\n String model;\n\n Car(this.color, this.model);\n\n void display() {\n print('Car Model: $model, Color: $color');\n }\n}<\/code><\/pre>\nCar<\/code>. This class has two properties, color<\/code> and model<\/code>, which are initialized through the constructor. The display<\/code> method prints the car’s information. Next, let’s create objects using this class.<\/p>\n3. Object and Instance<\/h2>\n
Car<\/code> class as follows:<\/p>\nvoid main() {\n Car car1 = Car('red', 'sports car');\n Car car2 = Car('blue', 'sedan');\n\n car1.display(); \/\/ Output: Car Model: sports car, Color: red\n car2.display(); \/\/ Output: Car Model: sedan, Color: blue\n}<\/code><\/pre>\nCar<\/code> objects named car1<\/code> and car2<\/code>. Each object stores the color and model information provided at creation, and we can output each car’s information by calling the display<\/code> method.<\/p>\n4. Various Components of a Class<\/h2>\n
4.1 Constructor<\/h3>\n
class Person {\n String name;\n int age;\n\n Person(this.name, this.age); \/\/ Default constructor\n\n Person.named(this.name, this.age); \/\/ Named constructor\n}<\/code><\/pre>\nPerson.named('John Doe', 30)<\/code>.<\/p>\n4.2 Method<\/h3>\n
class Animal {\n String name;\n\n Animal(this.name);\n\n void speak() {\n print('$name is making a sound.');\n }\n}<\/code><\/pre>\n4.3 Field<\/h3>\n
class Circle {\n static const double pi = 3.14; \/\/ Static variable\n double radius; \/\/ Instance variable\n\n Circle(this.radius);\n}<\/code><\/pre>\n4.4 Access Modifier<\/h3>\n
public<\/code> and private<\/code>. For example, prefixing a field with _<\/code> makes it private:<\/p>\nclass BankAccount {\n double _balance; \/\/ Private variable\n\n BankAccount(this._balance);\n\n void deposit(double amount) {\n _balance += amount;\n }\n\n double get balance => _balance; \/\/ Public method\n}<\/code><\/pre>\n5. Class Inheritance<\/h2>\n
class Vehicle {\n void start() {\n print('Vehicle started');\n }\n}\n\nclass Bike extends Vehicle {\n void ringBell() {\n print('Bicycle bell sound!');\n }\n}<\/code><\/pre>\nBike<\/code> class extends the Vehicle<\/code> class, meaning it can use the method start<\/code> from the Vehicle<\/code> class:<\/p>\nvoid main() {\n Bike bike = Bike();\n bike.start(); \/\/ Output: Vehicle started\n bike.ringBell(); \/\/ Output: Bicycle bell sound!\n}<\/code><\/pre>\n6. Polymorphism<\/h2>\n
class Shape {\n void draw() {\n print('Drawing a shape.');\n }\n}\n\nclass Circle extends Shape {\n @override\n void draw() {\n print('Drawing a circle.');\n }\n}\n\nclass Square extends Shape {\n @override\n void draw() {\n print('Drawing a square.');\n }\n}<\/code><\/pre>\n